Epithelial desquamation is a prominent pathological feature of acute lung injury, asthma, and other common pulmonary diseases, and elucidating the complex molecular mechanisms that regulate epithelial repair is essential to developing rational therapies. The current proposal addresses one potential mechanism by focusing on the function of matrilysin (MMP-7), a secreted matrix metalloproteinase (MMP), in lung epithelial cell migration. Although many proteinases, including MMPs, are expressed by injured epithelium, the specific functions and in vivo substrates have not been identified. Previous work has demonstrated that matrilysin expression is induced by lung injury in both airway and alveolar epithelium in humans and in mice, and that matrilysin activity facilitates lung epithelial cell migration during repair and promotes shedding of the extracellular ectodomain of the cell-cell junction protein E-cadherin from lung epithelium both in vitro and in vivo. Because remodeling of cell-cell junctions is necessary for epithelial cell migration, the proposed studies will test the hypothesis that matrilysin is delivered to cell-cell junctions in injured epithelium where it promotes cell migration by cleaving E-cadherin. Complementary morphological and biochemical strategies will be used to determine the molecular mechanisms of matrilysin action in lung epithelial cell migration and to verify these mechanisms in animal models of human disease. The studies in Specific Aim 1 will localize the spatial and temporal secretion of matrilysin in relationship to E-cadherin containing cell-cell junctions using both in vitro and in vivo models of epithelial injury and will characterize the morphological and structural changes in cell-cell junctions induced by matrilysin activity. The studies in Specific Aim 2 will assess directly whether E-cadherin is a substrate of matrilysin proteolytic activity by mapping cleavage sites in cell-free and cell-based assays. Specific Aim 3 will establish the specificity for E-cadherin cleavage by matrilysin in promoting cell-cell junction disassembly and cell migration. The results of these studies should provide new insights into MMP function in epithelial repair and form the basis for further investigations into the regulation of lung epithelial responses to injury. Working with William Parks, Ph.D., an established investigator in MMP biology and epithelial repair, Dr. McGuire will have the opportunity to develop experience and expertise in the application of basic techniques and approaches in molecular biology, cell biology, and protein biochemistry to fundamental questions in pulmonary biology.